1. Field of the Invention
The present invention relates to a developing apparatus for developing a photosensitive film provided on a substrate by supplying a developer.
2. Description of the Background Art
A developing apparatus is employed for developing a photosensitive film which is formed on a substrate such as a semiconductor wafer or a glass substrate for a liquid crystal display unit, a photomask or an optical disk.
For example, a rotary developing apparatus comprises a rotation holding part for horizontally holding a substrate and for rotating the same about a vertical axis, and a developer discharge nozzle for supplying a developer on the surface of the substrate. The developer discharge nozzle is mounted on the forward end of a nozzle arm which is rotatable in a horizontal plane, and can move between a position above the substrate and a buffer position.
In the development process, the developer discharge nozzle moves from the buffer position to the position above the substrate, and thereafter supplies the developer to a photosensitive film provided on the substrate. The supplied developer is spread on the overall surface of the substrate following rotation thereof, to be in contact with the photosensitive film. The substrate is maintained in a stationary state for a constant time while the developer is kept thereon by its surface tension (mounding), whereby the photosensitive film is developed. When completely supplying the developer, the developer discharge nozzle moves to the buffer position, separated from the position above the substrate, by rotation of the nozzle arm.
When the developer is exposed to the atmosphere in the vicinity of a discharge port of the developer discharge nozzle, moisture contained in the developer evaporates and changes the concentration of the developer, or the developer comes into contact with air and becomes denatured. In advance of the development, therefore, the developer discharge nozzle partially discharges the developer in the vicinity of the discharge port on the buffer position (predispense treatment), thereby homogenizing the developer stored therein.
In the aforementioned conventional rotary developing apparatus, however, the developer strikes the rotated substrate in an initial stage of discharge, and applies a remarkable impact to the photosensitive film provided on the substrate. This impact causes bubbles in the developer, and small bubbles remaining on the surface of the photosensitive film may result in defective development. Further, the photosensitive film may be damaged by the impact applied by the developer in the initial stage of discharge.
After the predispense treatment, the developer comes into contact with the air in the vicinity of the discharge port of the developer discharge nozzle which moves from the buffer position to the position above the substrate. Thus, there is a possibility that part of the developer supplied onto the substrate immediately after the start of discharge is slightly denatured as compared with developer which is continuously supplied thereafter. Thus, defective development may be caused on the substrate which is in contact with the developer immediately after the start of discharge. In addition, the developer may be dried due to contact with the air to cause particles to adhere onto the substrate.
Further, the developer dropped on the substrate is irregularly spread on the overall surface of the substrate due to centrifugal force. Thus, the developer must be supplied in a large quantity, to be homogenized on the substrate.